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Case definitions

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Each reporting health worker should be defining diseases in the same way, that is, they should all be using standard case definitions. These case definitions are not meant to define clinical diagnosis, but only to standardize what is reported to public health authorities. Of course, each emergency situation is different, so the diseases under surveillance as well as their case definitions may be different. Regardless, it is important that all reporting health workers in a specific population use the same case definitions.

Below is a list of case definitions from the World Health Organization for diseases common in humanitarian emergencies. (Click here to open the document containing these recommendations as well as a more complete discussion of communicable disease surveillance in emergencies.)

Acute lower respiratory tract infection in children less than 5 years of age

Cough or difficult breathing; and

Breathing 50 or more times per minute for infants aged 2 months to 1 year;

Breathing 40 or more times per minute for children aged 1 to 5 years

Acute watery diarrhoea

Three or more abnormally loose or fluid stools in the past 24 hours with or without dehydration.

Cholera - suspected

Person aged over 5 years with severe dehydration or death from acute watery diarrhoea with or without vomiting.

Person aged over 2 years with acute watery diarrhoea in an area where there is a cholera outbreak.

Cholera - confirmed

Isolation of Vibrio cholera O1 or O139 from diarrhoeal stool sample.

Bloody diarrhoea

Acute diarrhoea with visible blood in the stool.

Epidemic bacillary dysentery - confirmed

Bloody diarrhoea with isolation of Shigella dysenteriae from stool.

Malaria - suspected

Uncomplicated malaria

Patient with fever or history of fever within the past 48 hours (with or without other symptoms such as nausea, vomiting and diarrhoea, headache, back pain, chills, myalgia) in whom other obvious causes of fever have been excluded.

Severe malaria

Patient with symptoms as for uncomplicated malaria, as well as drowsiness with extreme weakness and associated signs and symptoms related to organ failure such as disorientation, loss of consciousness, convulsions, severe anaemia, jaundice, haemoglobinuria, spontaneous bleeding, pulmonary oedema and shock.

Malaria - confirmed

Demonstration of malaria parasites in blood film by examining thick or thin smears, or by rapid diagnostic test kit for Plasmodium falciparum.

Measles - suspected

Fever and maculopapular rash (i.e. non-vesicular) and cough, coryza (i.e. runny nose) or conjunctivitis (i.e. red eyes); or

Any person in whom a clinical health worker suspects measles infection.

Measles - confirmed

At least a fourfold increase in antibody titre or isolation of measles virus or presence of measles-specific IgM antibodies.

Meningitis - suspected

Sudden onset of fever (> 38.0 C axillary) and one of the following:

- neck stiffness,

- altered consciousness,

- other meningeal sign or petechial/purpural rash.

In children less than 1 year meningitis is suspected when fever is accompanied by a bulging fontanelle.

Meningitis - confirmed

Positive cerebrospinal fluid antigen detection or positive cerebrospinal fluid culture or positive blood culture.